The present invention relates generally to integrated optoelectronic circuit devices and integrated microwave devices and more particularly to a two-part optoelectronic circuit.
Optoelectronics pertains to the interaction of electronic processes with optical processes. This interaction is typically associated with energy conversion between electrical signals and optical signals. Optoelectronic devices, such as lasers, photodetectors, optical modulators, and optical switches, are examples of devices within which this interaction takes place.
Integration of optoelectronic/microwave modules has typically followed two paths, hybrid and monolithic. The hybrid integration connects discrete devices with electrical interconnects. Many individual devices are mounted separately on a carrier. Interconnections between the devices are typically accomplished through bond wires or metal paths formed on the carrier substrate. This approach has high flexibility since the devices are selected and interconnected according to the needs of a given application. However, this approach generally results in large circuit size and high parasitics relative to monolithic circuits. The advantage is that semiconductor materials and fabrication processes can be independently selected to enhance the performance of each device.
The hybrid approach is well suited for constructing prototypes. Production can be costly if the circuit contains many devices and interconnections. Additionally, the many separate devices must be tested and mounted individually.
Monolithic integration places all active and passive components on the same substrate. In addition to reducing the overall circuit size, this process reduces parasitic inductances and capacitances because it shortens the length of circuit interconnect structures. Monolithic circuits are typically formed with compound semiconductor families, for example, gallium aluminum arsenide (GaAlAs) and indium phosphide (InP), that inherently facilitate the realization of high resistivity substrates which reduce microwave losses and crosstalk in electrical interconnects.
The monolithic integration approach is particularly suited for high volume applications. Since many circuit chips can be obtained from a single wafer and several wafers can be processed in a given fabrication run, the cost of a fabrication run is shared among the many units produced. However, each integrated circuit is designed for a specific purpose. Therefore, different applications must be served by designing and fabricating entirely new chips. The tooling cost associated with each new application is high and may not be justifiable when small volumes are needed.
The present invention facilitates an application-specific rf-optoelectronic circuit by combining at least one generic chip, having common building-block components, with a defining substrate, having application-specific circuit parts and patterns. Thus, the same generic chip can be used in many different applications, and the defining substrate is specific to each application.
The generic chip contains building block components that perform functions such as, but not limited to, optical detection and generation, optical modulation, electrical switching and latching, and electrical amplification. The generic chip can be used in any application due to the fact that paths external to the generic chip connect the building block circuit parts on the generic chip.
The defining substrate consists of passive electronic and microwave components such as, but not limited to, capacitors, inductors, resistors and transmission line elements. These passive components provide electrical and optical interconnection between selected building block components on the generic chip and define the specific function of the combined chip/substrate circuit.
As an example, the components on the defining substrate can determine the gain, frequency response, input/output impedances, logic function, and optical interference according to the needs of a specific application. The defining substrate determines the overall function, so the same generic chip can be used in combination with different versions of defining substrates to perform a variety of application-specific functions.
It is an advantage of the present invention that prototype and production optoelectronic and rf circuits can be rapidly designed and fabricated. Another advantage is the reduced cost associated with using the same generic chip in many different applications. Yet another advantage is the flexibility to meet application specific needs simply by fabricating a defining substrate. Because the defining substrate contains only passive components, its fabrication is fairly quick and easy.
It is an object of the present invention to provide an application specific rf-optoelectronic circuit. It is another object of the present invention to maintain flexibility in the design and fabrication of the application specific rf-optoelectronic circuit. Yet another object of the present invention is to provide a two-part rf-optoelectronic circuit.
A further object of the present invention to use at least one generic chip in combination with a defining substrate, wherein the defining substrate determines the overall function of the circuit. Still a further object of the present invention is to maintain inexpensive and relatively fast fabrication of the application specific defining substrate.
Other advantages, objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.